I have decided to stop picking up the phone when I email someone and they immediately call me back. When someone does this, it means they encountered some detail that they didn't like, usually an instruction. Rather than follow said instruction, read the rest of the email, or god forbid take the time to digest the information contained within, they decide that it would be best to ramble in my ear about what they think I didn't understand. This isn't a generalization; it happens every single time. Pro tip: if by chance there actually is something I didn't understand, you're the one at fault for not properly communicating it in the first place. If I instead force the person to leave a voicemail or email me back, they will get to the point as quickly as possible. If someone in this situation leaves a voicemail that only asks that I call them back, I will complete all other pending requests first. It seems only fair.